1. Technical Field
The present disclosure is directed to tissue sealing and, in particular, to systems and methods for tissue sealing employing optical energy.
2. Background of Related Art
Existing energy-based surgical systems and methods use electrical energy or ultrasound energy to heat tissue (see, e.g., U.S. Pat. Nos. 7,384,420 and 7,255,697, and U.S. Patent Application Publication Nos. 2008/0147106 and 2009/0036912). For example, electrosurgical systems include an electrosurgical generator for producing high frequency electrical energy (e.g., radio frequency (RF) or microwave (MW) energy) and an electrosurgical instrument for applying the electrical energy to tissue. A surgeon may use the electrosurgical instrument to cut, coagulate, desiccate, and seal tissue.
Existing energy-based surgical methods and systems, however, may have several disadvantages that limit their performance and effectiveness. First, they may limit the surgeon's ability to control and localize energy in tissue. As a result, the energy thermally damages tissue adjacent to the target tissue. Also, energy is lost because an excessive volume of tissue is heated (i.e., both the target tissue and the adjacent tissue are heated).
Second, existing energy-based devices require direct physical contact between the tissue and the electrodes, ultrasound transducers, or sound-conducting portions of the surgical instrument to transmit energy to the tissue. As a result, a significant amount of energy is lost to the environment and to that portion of the instrument in contact with the heated tissue, while only a small amount of energy is used to actually heat tissue. Also, tissue may attach to that portion of the energy-based instrument that is in contact with the tissue.
Third, existing energy-based instruments may obstruct the surgeon's view of the target tissue or the operating site. Fourth, existing energy-based instruments typically include a large generator and a significant amount of wiring.
Lastly, electromagnetic energy-based systems and methods (e.g., RF- and MW-energy-based systems and methods) may cause stray currents, flashovers (e.g., an electric arc between the instrument and the tissue), short circuits in the conducting environment, and/or electromagnetic interference with other tissues and devices.
There are a number of laser-based surgical instruments, such as laser scalpels, that use laser radiation to cut and coagulate tissue. One disadvantage of laser scalpels is that they cannot seal relatively large vessels because laser scalpels cannot bring together opposite walls of the vessels. For example, in the article, Rodney A. White, et al., “Large vessel sealing with the argon laser,” Lasers in Surgery and Medicine 7, pages 229-235 (1987), the edges of damaged vessels are first approached to each other and then sealed by exposing them to laser radiation.
There are also devices that use light to perform tissue ablation procedures. For example*, as described in U.S. Pat. No. 4,266,547, tissue is placed between transparent holders through which the light is introduced to the tissue. The absorption of light by the tissue causes heating, charring, and ablation of the tissue. In optical ablation, the tissue can be illuminated with propagating waves or evanescent waves resulting from total external reflection. See, e.g., Cox, et al., “New method for exposing mammalian cells to intense laser radiation using the evanescent fields created in optical waveguides,” Med. Phys. 5:274-279 (1978).
There are also instruments for coagulating blood vessels through the skin without deforming or damaging the tissue. For example, U.S. Pat. No. 7,452,355 describes simultaneously using multiple wavelengths of light radiation so that the radiation of one of the wavelengths modifies the blood and creates in the blood centers of high absorption of the radiation of other wavelengths, which can penetrate deeper into the tissue and completely seal the vessel.
The optical methods and systems described above, however, may not provide high quality vascular tissue sealing, especially for relatively large vessels.